For I will pass through the land of Egypt uses a verb meaning to “go through” a territory, passing from one side to the other. Here the entire country of Egypt is meant. So one may also express this as “I will go through the whole land of Egypt.” That night refers to the “same night” (New American Bible, Contemporary English Version) mentioned in verse 8. (See 11.4.) And I will smite is a verb meaning to strike or hit, not necessarily to kill. (The same word is used three times in 2.11-13.) New Revised Standard Version has changed smite to “strike down,” along with New Jewish Publication Society’s Tanakh, New International Version, New Jerusalem Bible, and others. The context, however, suggests “killing,” so many translations, including Revised Standard Version, Good News Translation, and Contemporary English Version, follow this interpretation. (In 4.23 a different verb clearly means “slay.”)

All the first-born in the land of Egypt should be understood as the first male child of all Egyptian fathers, as explained at 11.5. Both man and beast includes the first-born of the Egyptians’ animals as well. Another way to render this is “the firstborn son in every Egyptian family, along with the firstborn males of all animals.”

And on all the gods of Egypt, which follows a major break in the verse, includes the Pharaoh, who was also considered divine along with the many gods worshiped by the Egyptians. But this does not imply that the Pharaoh himself or the Egyptian gods would be killed. The word on really goes with the following verb, meaning to execute judgments on.

I will execute judgments is literally “I will do judgments.” Judgments is plural and can also mean “punishments” (New Jewish Publication Society’s Tanakh). Here it probably means the same as the “great acts of judgment” in 6.6 (literally “great judgments”), referring to all the plagues brought upon Egypt. Alternative translation models are “I will punish the gods of Egypt in many ways,” or even “I will severely punish the gods of Egypt.”

The word for gods is ʾelohim, the same word for Israel’s God, so there is no clear indication here that the gods of Egypt were false gods, or even nonexistent; but in many languages a term such as “small gods” must be used (see the discussion below). What is clear is that Yahweh will “mete out punishments” (New Jewish Publication Society’s Tanakh) on all the Egyptian gods and prove himself more powerful. This is emphasized by the self-introductory formula, I am the LORD. A Handbook on the Books of Nahum, Habakkuk, and Zephaniah, page 20, has an excellent discussion on the translation of “god” versus “God”:
In English the supreme God is differentiated from lesser gods or deities by the use of a capital letter. In many other languages this device is not suitable, or the term for God is only used for the Christian God, so it will seem strange to refer to other gods. There are two possible solutions. Translators may use a term or terms which refer to supernatural beings which non-Christians in the culture worship, or they may use the term for the Christian God with an adjective; for example, “false gods” or even “small gods.” This will show that these are beings which are thought to be like God but are not really God.

Since this formula has no verb (literally “I Yahweh”), some consider it to be in apposition with I will smite. So Revised English Bible has “Thus I shall execute judgement, I the LORD, against all the gods of Egypt.” (Similar are New Jewish Publication Society’s Tanakh, New American Bible, and New Jerusalem Bible.) However, in languages where apposition is not natural, a simpler rendering will be preferred; for example, “I am Yahweh, and I will severely punish the gods of the Egyptians” or “… the gods whom the Egyptians worship.”

In a number of languages translators will find Good News Translation‘s model unnatural style because of its one long compound sentence. An alternative model dividing the verse into three sentences is:

• On that same night I will go through the entire land of Egypt. I will kill the firstborn sons in every Egyptian family, along with the firstborn males of all the animals. I am Yahweh, and I will severely punish all the gods [or, false gods] whom the Egyptians worship.

Quoted with permission from Osborn, Noel D. and Hatton, Howard A. A Handbook on Exodus. (UBS Helps for Translators). New York: UBS, 1999. For this and other handbooks for translators see here .